Integrated touch screen

ABSTRACT

In one embodiment, an apparatus includes a display stack for a touch-sensitive screen. The display stack comprises a plurality of layers in which a top layer comprises a substantially transparent cover layer. The display stack is configured to display a color image. The apparatus also includes a touch sensor provided within the display stack. The touch sensor comprises a plurality of first conductive electrodes contacting a layer of a subset of the plurality of layers of the display stack. The subset of the plurality of layers is below the substantially transparent cover layer. The touch sensor also includes a plurality of second conductive electrodes contacting a layer of the subset of the plurality of layers.

RELATED APPLICATION

This application claims the benefit, under 35 U.S.C. §119(e), of U.S.Provisional Patent Application No. 61/563,007 filed 22 Nov. 2011.

TECHNICAL FIELD

This disclosure generally relates to touch screens.

BACKGROUND

A touch sensor may detect the presence and location of a touch or theproximity of an object (such as a user's finger or a stylus) within atouch-sensitive area of the touch sensor overlaid on a display screen,for example. In a touch-sensitive-display application, the touch sensormay enable a user to interact directly with what is displayed on thescreen, rather than indirectly with a mouse or touch pad. A touch sensormay be attached to or provided as part of a desktop computer, laptopcomputer, tablet computer, personal digital assistant (PDA), smartphone,satellite navigation device, portable media player, portable gameconsole, kiosk computer, point-of-sale device, or other suitable device.A control panel on a household or other appliance may include a touchsensor.

A display screen includes a number of layers that form a display stack.The layers of the display stack enable the display screen to produce acolor image. The number and type of layers depends on the type ofdisplay screen. For example, a Liquid Crystal Display (LCD) baseddisplay screen has different layers than an Organic Light Emitting Diode(OLED) based display screen. To form a touch screen, a touch sensor istypically placed over the display stack. For example, the touch sensormay be formed on a transparent cover. The transparent cover, with thetouch sensor, is then placed over an already formed display stack. Thisarrangement negatively impacts the contrast ratio of the display screen.For example, there is typically an air gap between the display stack andthe sensor which can create undesirable reflections.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example touch sensor with an example controller.

FIG. 2 illustrates a block diagram of a touch sensor provided within adisplay stack.

FIG. 3 illustrates a single sided touch sensor in which the electrodesare located on the bottom surface of a polarizer of an LCD displaystack.

FIG. 4 illustrates a single sided touch sensor in which the electrodesare located on the top surface of a glass layer of an OLED displaystack.

FIG. 5 illustrates a double sided touch sensor in which the electrodesare located on a top and bottom surface of a color filter layer of anLCD display stack.

FIG. 6 illustrates a single sided touch sensor in which the electrodesare located on a non-birefringent layer below the polarizer of an LCDdisplay stack.

DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1 illustrates an example touch sensor 10 with an exampletouch-sensor controller 12. Touch sensor 10 and touch-sensor controller12 may detect the presence and location of a touch or the proximity ofan object within a touch-sensitive area of touch sensor 10. Herein,reference to a touch sensor may encompass both the touch sensor and itstouch-sensor controller, where appropriate. Similarly, reference to atouch-sensor controller may encompass both the touch-sensor controllerand its touch sensor, where appropriate. Touch sensor 10 may include oneor more touch-sensitive areas, where appropriate. Touch sensor 10 mayinclude an array of drive and sense electrodes (or an array ofelectrodes of a single type) disposed on one or more substrates, whichmay be made of a dielectric material and/or may be included in a displaystack. Herein, reference to a touch sensor may encompass both theelectrodes of the touch sensor and the substrate(s) that they aredisposed on, where appropriate. Alternatively, where appropriate,reference to a touch sensor may encompass the electrodes of the touchsensor, but not the substrate(s) that they are disposed on.

An electrode (whether a drive electrode or a sense electrode) may be anarea of conductive material forming a shape, such as for example a disc,square, rectangle, thin line, other suitable shape, or suitablecombination of these. One or more cuts in one or more layers ofconductive material may (at least in part) create the shape of anelectrode, and the area of the shape may (at least in part) be boundedby those cuts. In particular embodiments, the conductive material of anelectrode may occupy approximately 100% of the area of its shape. As anexample and not by way of limitation, an electrode may be made of indiumtin oxide (ITO) and the ITO of the electrode may occupy approximately100% of the area of its shape (sometimes referred to as 100% fill),where appropriate. In particular embodiments, the conductive material ofan electrode may occupy substantially less than 100% of the area of itsshape. As an example and not by way of limitation, an electrode may bemade of fine lines of metal or other conductive material (FLM) such asfor example copper, silver, or a copper- or silver-based material andthe fine lines of conductive material may occupy approximately 5% of thearea of its shape in a hatched, mesh, or other suitable pattern. Herein,reference to FLM encompasses such material, where appropriate. Althoughthis disclosure describes or illustrates particular electrodes made ofparticular conductive material forming particular shapes with particularfills having particular patterns, this disclosure contemplates anysuitable electrodes made of any suitable conductive material forming anysuitable shapes with any suitable fill percentages having any suitablepatterns.

Where appropriate, the shapes of the electrodes (or other elements) of atouch sensor may constitute in whole or in part one or moremacro-features of the touch sensor. One or more characteristics of theimplementation of those shapes (such as, for example, the conductivematerials, fills, or patterns within the shapes) may constitute in wholeor in part one or more micro-features of the touch sensor. One or moremacro-features of a touch sensor may determine one or morecharacteristics of its functionality, and one or more micro-features ofthe touch sensor may determine one or more optical features of the touchsensor, such as transmittance, refraction, or reflection.

A mechanical stack may contain the substrate (or multiple substrates)and the conductive material forming the drive or sense electrodes oftouch sensor 10. In some embodiments, the mechanical stack may be withinor comprise a display stack configured to generate images. As an exampleand not by way of limitation, the mechanical stack may include a firstlayer of optically clear adhesive (OCA) beneath a cover panel of adisplay stack. The cover panel may be clear and made of a resilientmaterial suitable for repeated touching, such as for example glass,polycarbonate, or poly(methyl methacrylate) (PMMA). This disclosurecontemplates any suitable cover panel made of any suitable material. Thefirst layer of OCA may be disposed between a layer or substrate of thedisplay stack and the substrate with the conductive material forming thedrive or sense electrodes. The substrate with the conductive materialmay provide a benefit or feature in producing an image (e.g., it may bea layer or substrate found in a typical, non-touch, display stack) or itmay be a layer added specifically to provide a substrate on which theelectrodes are formed. In some embodiments, the mechanical stack mayalso include a second layer of OCA. In some embodiments, the mechanicalstack may also include a dielectric layer (which may be made ofpolyethylene terephthalate (PET) or another suitable material, similarto the substrate with the conductive material forming the drive or senseelectrodes). As an alternative, where appropriate, a thin coating of adielectric material may be applied instead of the second layer of OCAand/or the dielectric layer. The second layer of OCA may be disposedbetween the substrate with the conductive material making up the driveor sense electrodes and the dielectric layer, and the dielectric layermay be disposed between the second layer of OCA and another layer of thedisplay stack. As an example only and not by way of limitation, thecover panel may have a thickness of approximately 1 mm; the first layerof OCA may have a thickness of approximately 0.05 mm; the substrate withthe conductive material forming the drive or sense electrodes may have athickness of approximately 0.05 mm; the second layer of OCA may have athickness of approximately 0.05 mm; and the dielectric layer may have athickness of approximately 0.05 mm. Although this disclosure describes aparticular mechanical stack with a particular number of particularlayers made of particular materials and having particular thicknesses,this disclosure contemplates any suitable mechanical stack with anysuitable number of any suitable layers made of any suitable materialsand having any suitable thicknesses.

In particular embodiments, the drive or sense electrodes in touch sensor10 may be made of ITO in whole or in part. In particular embodiments,the drive or sense electrodes in touch sensor 10 may be made of finelines of metal or other conductive material. As an example and not byway of limitation, one or more portions of the conductive material maybe copper or copper-based and have a thickness of approximately 5 μm orless and a width of approximately 10 μm or less. As another example, oneor more portions of the conductive material may be silver orsilver-based and similarly have a thickness of approximately 5 μm orless and a width of approximately 10 μm or less. This disclosurecontemplates any suitable electrodes made of any suitable material.

Touch sensor 10 may implement a capacitive form of touch sensing. In amutual-capacitance implementation, touch sensor 10 may include an arrayof drive and sense electrodes forming an array of capacitive nodes. Adrive electrode and a sense electrode may form a capacitive node. Thedrive and sense electrodes forming the capacitive node may come neareach other, but not make electrical contact with each other. Instead,the drive and sense electrodes may be capacitively coupled to each otheracross a space between them. A pulsed or alternating voltage applied tothe drive electrode (by touch-sensor controller 12) may induce a chargeon the sense electrode, and the amount of charge induced may besusceptible to external influence (such as a touch or the proximity ofan object). When an object touches or comes within proximity of thecapacitive node, a change in capacitance may occur at the capacitivenode and touch-sensor controller 12 may measure the change incapacitance. By measuring changes in capacitance throughout the array,touch-sensor controller 12 may determine the position of the touch orproximity within the touch-sensitive area(s) of touch sensor 10.

In a self-capacitance implementation, touch sensor 10 may include anarray of electrodes of a single type that may each form a capacitivenode. When an object touches or comes within proximity of the capacitivenode, a change in self-capacitance may occur at the capacitive node andtouch-sensor controller 12 may measure the change in capacitance, forexample, as a change in the amount of charge needed to raise the voltageat the capacitive node by a pre-determined amount. As with amutual-capacitance implementation, by measuring changes in capacitancethroughout the array, touch-sensor controller 12 may determine theposition of the touch or proximity within the touch-sensitive area(s) oftouch sensor 10. This disclosure contemplates any suitable form ofcapacitive touch sensing, where appropriate.

In particular embodiments, one or more drive electrodes may togetherform a drive line running horizontally or vertically or in any suitableorientation. Similarly, one or more sense electrodes may together form asense line running horizontally or vertically or in any suitableorientation. In particular embodiments, drive lines may runsubstantially perpendicular to sense lines. Herein, reference to a driveline may encompass one or more drive electrodes making up the driveline, and vice versa, where appropriate. Similarly, reference to a senseline may encompass one or more sense electrodes making up the senseline, and vice versa, where appropriate.

Touch sensor 10 may have drive and sense electrodes disposed in apattern on one side of a single substrate. In such a configuration, apair of drive and sense electrodes capacitively coupled to each otheracross a space between them may form a capacitive node. For aself-capacitance implementation, electrodes of only a single type may bedisposed in a pattern on a single substrate. In addition or as analternative to having drive and sense electrodes disposed in a patternon one side of a single substrate, touch sensor 10 may have driveelectrodes disposed in a pattern on one side of a substrate and senseelectrodes disposed in a pattern on another side of the substrate.Moreover, touch sensor 10 may have drive electrodes disposed in apattern on one side of one substrate and sense electrodes disposed in apattern on one side of another substrate. In such configurations, anintersection of a drive electrode and a sense electrode may form acapacitive node. Such an intersection may be a location where the driveelectrode and the sense electrode “cross” or come nearest each other intheir respective planes. The drive and sense electrodes do not makeelectrical contact with each other—instead they are capacitively coupledto each other across a dielectric at the intersection. Although thisdisclosure describes particular configurations of particular electrodesforming particular nodes, this disclosure contemplates any suitableconfiguration of any suitable electrodes forming any suitable nodes.Moreover, this disclosure contemplates any suitable electrodes disposedon any suitable number of any suitable substrates in any suitablepatterns.

As described above, a change in capacitance at a capacitive node oftouch sensor 10 may indicate a touch or proximity input at the positionof the capacitive node. Touch-sensor controller 12 may detect andprocess the change in capacitance to determine the presence and locationof the touch or proximity input. Touch-sensor controller 12 may thencommunicate information about the touch or proximity input to one ormore other components (such one or more central processing units (CPUs))of a device that includes touch sensor 10 and touch-sensor controller12, which may respond to the touch or proximity input by initiating afunction of the device (or an application running on the device)associated with it. Although this disclosure describes a particulartouch-sensor controller having particular functionality with respect toa particular device and a particular touch sensor, this disclosurecontemplates any suitable touch-sensor controller having any suitablefunctionality with respect to any suitable device and any suitable touchsensor.

Touch-sensor controller 12 may be one or more integrated circuits (ICs),such as for example general-purpose microprocessors, microcontrollers,programmable logic devices or arrays, or application-specific ICs(ASICs). In particular embodiments, touch-sensor controller 12 comprisesanalog circuitry, digital logic, and digital non-volatile memory. Inparticular embodiments, touch-sensor controller 12 is disposed on aflexible printed circuit (FPC) bonded to the substrate of touch sensor10. The FPC may be active or passive, where appropriate. In particularembodiments, multiple touch-sensor controllers 12 are disposed on theFPC. Touch-sensor controller 12 may include a processor unit, a driveunit, a sense unit, and a storage unit. The drive unit may supply drivesignals to the drive electrodes of touch sensor 10. The sense unit maysense charge at the capacitive nodes of touch sensor 10 and providemeasurement signals to the processor unit representing capacitances atthe capacitive nodes. The processor unit may control the supply of drivesignals to the drive electrodes by the drive unit and processmeasurement signals from the sense unit to detect and process thepresence and location of a touch or proximity input within thetouch-sensitive area(s) of touch sensor 10. The processor unit may alsotrack changes in the position of a touch or proximity input within thetouch-sensitive area(s) of touch sensor 10. The storage unit may storeprogramming for execution by the processor unit, including programmingfor controlling the drive unit to supply drive signals to the driveelectrodes, programming for processing measurement signals from thesense unit, and other suitable programming, where appropriate. Althoughthis disclosure describes a particular touch-sensor controller having aparticular implementation with particular components, this disclosurecontemplates any suitable touch-sensor controller having any suitableimplementation with any suitable components.

Tracks 14 of conductive material disposed on the substrate of touchsensor 10 may couple the drive or sense electrodes of touch sensor 10 toconnection pads 16, also disposed on the substrate of touch sensor 10.As described below, connection pads 16 facilitate coupling of tracks 14to touch-sensor controller 12. Tracks 14 may extend into or around (e.g.at the edges of) the touch-sensitive area(s) of touch sensor 10.Particular tracks 14 may provide drive connections for couplingtouch-sensor controller 12 to drive electrodes of touch sensor 10,through which the drive unit of touch-sensor controller 12 may supplydrive signals to the drive electrodes. Other tracks 14 may provide senseconnections for coupling touch-sensor controller 12 to sense electrodesof touch sensor 10, through which the sense unit of touch-sensorcontroller 12 may sense charge at the capacitive nodes of touch sensor10. Tracks 14 may be made of fine lines of metal or other conductivematerial. As an example and not by way of limitation, the conductivematerial of tracks 14 may be copper or copper-based and have a width ofapproximately 100 μm or less. As another example, the conductivematerial of tracks 14 may be silver or silver-based and have a width ofapproximately 100 μm or less. In particular embodiments, tracks 14 maybe made of ITO in whole or in part in addition or as an alternative tofine lines of metal or other conductive material. Although thisdisclosure describes particular tracks made of particular materials withparticular widths, this disclosure contemplates any suitable tracks madeof any suitable materials with any suitable widths. In addition totracks 14, touch sensor 10 may include one or more ground linesterminating at a ground connector (which may be a connection pad 16) atan edge of the substrate of touch sensor 10 (similar to tracks 14).

Connection pads 16 may be located along one or more edges of thesubstrate, outside the touch-sensitive area(s) of touch sensor 10. Asdescribed above, touch-sensor controller 12 may be on an FPC. Connectionpads 16 may be made of the same material as tracks 14 and may be bondedto the FPC using an anisotropic conductive film (ACF). Connection 18 mayinclude conductive lines on the FPC coupling touch-sensor controller 12to connection pads 16, in turn coupling touch-sensor controller 12 totracks 14 and to the drive or sense electrodes of touch sensor 10. Thisdisclosure contemplates any suitable connection 18 between touch-sensorcontroller 12 and touch sensor 10.

FIG. 2 illustrates a block diagram of touch sensor 22 provided withindisplay stack 21, in accordance with particular embodiments. Displaystack 21 may comprise a plurality of layers configured to generate acolor image. The type and number of layers within display stack 21 mayvary depending on the type of display stack and/or the intendedapplication of the display stack. For example, an LCD based displaystack 21 may include two or more polarizers while an OLED based displaystack may include only one, or no, polarizers. Each layer may comprise aparticular feature or characteristic used in a display stack forgenerating an image. These layers may in some embodiments, be configuredto provide a color image. Particular embodiments contemplate displaystack 21 comprising any number and/or type of layers for any type ofdisplay. In some embodiments, display stack 21 may be a flexible displaystack. In some embodiments, display stack 21 may comprise a curvedsurface (as opposed to the straight surface depicted in FIGS. 3 through6).

One or more components of touch sensor 22 may be integrated into displaystack 21 in any of a variety of different ways, depending on operationalneeds or the particular embodiment. Touch sensor 22 may be located inany of a variety of different locations within display stack 21. Thelocation of touch sensor 22 may vary depending on the type of displaystack 21 (e.g., an LCD display, OLED display, etc.). For example, in anLCD display in which display stack 21 includes one or more polarizers,touch sensor 22 may be positioned within display stack 21 so as to notalter the polarization of the light before it passes through one or moreof the polarizers. For example in an LCD display stack 21, if touchsensor 22 includes a substrate made of a birefringent material, thentouch sensor 22 may be positioned above any polarizers within displaystack 21. If touch sensor 22 includes a substrate made of anon-birefringent material, touch sensor 22 may be positioned between thepolarizers of display stack 21. As another example, in an OLED displaystack 21, it may not matter whether or not touch sensor 22 uses abirefringent material. This may allow touch sensor 22 to be positionedwithin any appropriate location within display stack 21. As yet anotherexample, in some embodiments touch sensor 22 may use an existing layer(e.g., a layer found in a typical non-touch display stack, such as thecolor filter layer or one of the polarizer layers, etc.) of displaystack 21 as its substrate.

Touch sensor 22 may be similar to, and comprise similar components andfunctionality, as touch sensor 10 described above with respect toFIG. 1. Depending on the embodiment, and/or operational needs, touchsensor 22 may be a laminated layer within display stack 21, or one ormore of the components of touch sensor 22 (e.g., fine line metalelectrodes for sensing a touch input) may be deposited on an existinglayer of display stack 21. This may allow the touch sensingfunctionality to be included during the manufacturing of display stack21. In embodiments in which touch sensor 22 is deposited on an existinglayer of display stack 21, the existing layer of display stack 21 mayfunction as the substrate for touch sensor 22. In other embodiments,touch sensor 22 may comprise its own substrate that is placed withindisplay stack 21. Depending on the type of display and/or the desiredlocation of touch sensor 22 within display stack, the substrate used fortouch sensor 21 may be made of a birefringent material or anon-birefringent material. In certain embodiments, having touch sensor22 within display stack 21 allows for a display stack with touch sensingcapability that is substantially free of any air gaps between touchsensor 22 and display stack 21. As such, in certain embodiments, havingtouch sensor 22 within display stack 21 allows for a display stack withtouch sensing capability that is thinner than a traditional displaystack with a touch sensor added on top of the display stack.

FIGS. 3 through 6 depict various embodiments illustrating differentlocations of the electrodes of a touch sensor within a display stack,different types of touch sensors, and different types of display stacks.The illustrated embodiments are not intended to be exhaustive of allpossible combinations. For example, one embodiment that may be withinthe scope of the claims but is not depicted may comprise a double sidedsensor in which electrodes are deposited on either side of a colorfilter of an OLED. Other configurations and embodiments are within thescope of the appended claims and are contemplated by the inventors.

FIG. 3 illustrates a single-sided touch sensor in which the electrodesare located on the bottom surface of a polarizer of an LCD displaystack, in accordance with particular embodiments. Display stack 100includes cover panel 110, polarizer 115, color filter glass 120, colorfilter 125, reference voltage layer 130, liquid crystal 135, conductivelayer 140, rear glass 145, polarizer 150, backlight source 155, senseelectrodes 165, and drive electrodes 170. One or more adhesive layers(e.g., OCA) may be used in display stack 100 to bind layers to oneanother. The depicted embodiment illustrates some adhesive layers, butnot necessarily all, adhesive layers. The depicted layers maycumulatively form a display stack of a display screen with integratedtouch functionality.

Cover panel 110 may be a transparent surface designed to withstandrepeated touching from a user. In some embodiments, cover panel 110 maybe similar to the top layer of a typical display stack or a typicaltouch screen. In the depicted embodiment, cover panel 110 is part of thedisplay stack of the touch screen. This is in contrast to a typicaltouch screen in which the cover panel is separate from the display stackand there is a small air gap between the cover panel and the displaystack. In the depicted embodiment, cover panel 110 may be clear and madeof a resilient material suitable for repeated touching, such as forexample glass, polycarbonate, or poly(methyl methacrylate) (PMMA). Thisdisclosure contemplates any suitable cover panel made of any suitablematerial.

In the depicted embodiment, sense and drive electrodes 165 and 170 areused to determine the position of a touch input on the touch screen. Thetouch input may be received from any of a variety of sources including,but not limited to, one or more fingers or a stylus. In the depictedembodiment, both electrodes 165 and 170 are located on the same side ofpolarizer 115. In the depicted embodiment, sense electrodes 165 anddrive electrodes 170 are deposited on the bottom surface of polarizer115. In some embodiments, sense electrodes 165 and drive electrodes 170may comprise fine lines of metal deposited on polarizer 115. In thedepicted embodiments, polarizer 115 acts as a substrate for the touchsensor, including sense electrode 165 and drive electrode 170. This mayreduce the overall thickness of a touch screen using display stack 100by removing the use of a separate substrate specifically for the senseelectrodes 165 and drive electrodes 170. Using an existing layer (e.g.,polarizer 115) of display stack 100 may improve image quality byreducing the number of layers light has to travel through. In someembodiments, sense electrodes 165 and drive electrodes 170 may bedeposited on a separate touch sensor substrate (not depicted) that isadded within display stack 100. In some embodiments, sense electrodes165 and drive electrodes 170 and the touch substrate may be laminated ontop of polarizer 115. If the sense electrodes 165 and drive electrodes170 are positioned above polarizer 115, it may not be necessary to use anon-birefringent material for the touch sensor substrate. An adhesivelayer may provide adhesion for layers added on top of sense electrodes165 and drive electrodes 170.

FIG. 4 illustrates a single-sided touch sensor in which the electrodesare located on the top surface of a glass layer of an OLED displaystack, in accordance with particular embodiments. OLED display stack 200includes cover panel 210, color filter glass 220, color filter 225,conductive layer 230, organic light emitting diode (OLED) layer 235,conductive layer 240, and rear glass 245. One or more adhesive layers(e.g., OCA) may be used in display stack 100 to bind layers to oneanother. The depicted embodiment illustrates some adhesive layers, butnot necessarily all, adhesive layers. In the depicted embodiment, senseelectrodes 265 and drive electrodes 270 are both located along the topsurface of color filter glass 220. They may be deposited or laminatedthereon.

In some embodiments, sense electrodes 265 and drive electrodes 270 maybe located on a touch sensor substrate (not depicted) added to displaystack 200. Because display stack 200 is an OLED, the material used forthe touch sensor, (e.g., non-birefringent or birefringent) may be ofless importance than with an LCD. That is, any polarizing effect of theadded touch sensor substrate may not negatively impact the non-polarizedlight coming from OLED 235. Depending on the embodiment or configurationof the OLED display device, display stack 200 may be flexible or rigid.In addition, display stack 200 may be straight (as depicted) or curved.In some embodiments, sense electrodes 265 and drive electrodes 270 maycomprise fine line metal. In other embodiments, sense electrodes 265 anddrive electrodes 270 may be formed from indium tin oxide (ITO).

FIG. 5 illustrates a double-sided touch sensor in which the electrodesare located on a top and bottom surface of a color filter layer of anLCD display stack, in accordance with particular embodiments. Displaystack 300 includes cover panel 310, polarizer 315, LCD cover glass 320,color filter 325, reference voltage layer 330, liquid crystal 335,conductive layer 340, rear glass 345, polarizer 350, backlight source355, sense electrodes 365, and drive electrodes 370. One or moreadhesive layers (e.g., OCA) may be used in display stack 100 to bindlayers to one another. The depicted embodiment illustrates some adhesivelayers, but not necessarily all adhesive layers. In the depictedembodiment, sense electrodes are located on a top surface of colorfilter 325 and drive electrode 370 is located on a bottom surface ofcolor filter 325. As can be seen in FIG. 5, sense electrodes 365 anddrive electrode 370 are located on either side of an existing layer(color filter 325) of display stack 300. In the depicted embodimentcolor filter 325 acts as a substrate for sense electrodes 365 and driveelectrodes 370. Depending on the topology of display stack 300, senseelectrodes 365 and drive electrode 370 may be deposited on color filterlayer 325. Because sense electrodes 365 and drive electrode 370 arelocated on an existing layer of display stack 300, the resulting touchfunctionality of display stack 300 may be thinner than a traditional LCDtouch screen.

FIG. 6 illustrates a single-sided touch sensor in which the electrodesare located on a non-birefringent layer below the polarizer of an LCDdisplay stack. Display stack 400 includes cover panel 410, polarizer415, color filter glass 420, color filter 425, reference voltage layer430, liquid crystal 435, conductive layer 440, rear glass 445, polarizer450, backlight source 455, sense electrodes 465, drive electrodes 470,non-birefringent layer 480. One or more adhesive layers (e.g., OCA) maybe used in display stack 100 to bind layers to one another. The depictedembodiment illustrates some adhesive layers, but not necessarily all,adhesive layers.

The layers of display stack 100 may be similar to the layers of displaystack 100 depicted in FIG. 3. One difference may be the inclusion of anadditional layer, non-birefringent layer 480. As mentioned in previousfigures, in some embodiments, an additional layer may be added to thedisplay stack to serve as the substrate for the touch sensor. In FIG. 6,display stack 400 includes non-birefringent layer 480. Non-birefringentlayer 480 provides a substrate on which sense electrodes 465 and driveelectrodes 470 may be located. The electrodes may be deposited orlaminated on non-birefringent layer 480. Because non-birefringent layer480 is non-birefringent, it does not twist or otherwise re-polarize thealready polarized light prior to passing through polarizer 415.

While FIGS. 3 through 6 have depicted various locations andconfiguration of touch sensor electrodes within different types ofdisplay stacks, one skilled in the art would appreciate that anyconfiguration of touch sensors may be located in any suitable positionwithin the display stack. Depending on the embodiment, the touch sensorsmay be deposited on, or laminated to, any suitable layer within adisplay stack. By way of example, and not by way of limitation,particular embodiments may comprise a touch sensor located under alinear and/or circular polarizer; a touch sensor located above thelinear and/or circular polarizer; a touch sensor patterned on a linearand/or circular polarizer substrate; a touch sensor patterned under alinear and/or circular polarizer substrate; a touch sensor patterned onbirefringent free material; a touch sensor patterned above and/or belowa color filter layer; any of the above with a single sided sensor on onesurface, where appropriate; any of the above with a dual sided sensor onboth surfaces, where appropriate; any of the above with an AR layer;and/or any of the above with an AG layer. In certain embodiments,patterning the sensor on any optical component included within a displaystack (e.g., polarizers, filters etc) may reduce the overall thicknessof a touch screen and may increase transmissivity as there is noseparate substrate for the touch sensor through which light must travel.In particular embodiments, in addition to reducing reflected light fromthe touch electrodes, reflected light from other internal surfaces maybe reduced. This may increase the effective contrast ratio of the LCD toambient light—making the LCD more visible in direct sunlight orconversely reducing the required intensity of light from the LCD for agiven contrast ratio (power saving).

Moreover, if a non-birefringent substrate, or any other additionalsubstrate for the touch sensor, is added to the display stack, such alayer may be deposited or formed anywhere within the display stack. Byincorporating the touch sensor, in any of the various locations, withinthe display stack, the manufacturing process may be simplified and theoverall thickness of a touch screen may be reduced. The reduction isparticularly evident where one of the existing layers of a traditionaldisplay stack is used as the substrate for the touch sensor.Furthermore, in particular embodiments, by locating the touch sensorwithin the display stack, the touch screen may be free of air gaps. Thismay improve the image quality (e.g., improve the perceived contrastratio) of a touch screen.

Although this disclosure describes a particular mechanical stack andparticular display stacks with particular numbers of particular layersmade of particular materials and having particular thicknesses, thisdisclosure contemplates any suitable mechanical stack and/or displaywith any suitable number of any suitable layers made of any suitablematerials and having any suitable thicknesses.

Herein, reference to a computer-readable storage medium encompasses oneor more non-transitory, tangible computer-readable storage mediapossessing structure. As an example and not by way of limitation, acomputer-readable storage medium may include a semiconductor-based orother integrated circuit (IC) (such, as for example, afield-programmable gate array (FPGA) or an application-specific IC(ASIC)), a hard disk, an HDD, a hybrid hard drive (HHD), an opticaldisc, an optical disc drive (ODD), a magneto-optical disc, amagneto-optical drive, a floppy disk, a floppy disk drive (FDD),magnetic tape, a holographic storage medium, a solid-state drive (SSD),a RAM-drive, a SECURE DIGITAL card, a SECURE DIGITAL drive, or anothersuitable computer-readable storage medium or a combination of two ormore of these, where appropriate. Herein, reference to acomputer-readable storage medium excludes any medium that is noteligible for patent protection under 35 U.S.C. §101. Herein, referenceto a computer-readable storage medium excludes transitory forms ofsignal transmission (such as a propagating electrical or electromagneticsignal per se) to the extent that they are not eligible for patentprotection under 35 U.S.C. §101. A computer-readable non-transitorystorage medium may be volatile, non-volatile, or a combination ofvolatile and non-volatile, where appropriate.

Herein, “or” is inclusive and not exclusive, unless expressly indicatedotherwise or indicated otherwise by context. Therefore, herein, “A or B”means “A, B, or both,” unless expressly indicated otherwise or indicatedotherwise by context. Moreover, “and” is both joint and several, unlessexpressly indicated otherwise or indicated otherwise by context.Therefore, herein, “A and B” means “A and B, jointly or severally,”unless expressly indicated otherwise or indicated otherwise by context.

This disclosure encompasses all changes, substitutions, variations,alterations, and modifications to the example embodiments herein that aperson having ordinary skill in the art would comprehend. Particularfeatures discussed with respect to particular embodiments may becombined or omitted from the features of other embodiments, whereappropriate. Moreover, reference in the appended claims to an apparatusor system or a component of an apparatus or system being adapted to,arranged to, capable of, configured to, enabled to, operable to, oroperative to perform a particular function encompasses that apparatus,system, component, whether or not it or that particular function isactivated, turned on, or unlocked, as long as that apparatus, system, orcomponent is so adapted, arranged, capable, configured, enabled,operable, or operative.

What is claimed is:
 1. An apparatus comprising: a display stack for atouch-sensitive screen, the display stack comprising a plurality oflayers in which a top layer comprises a substantially transparent coverlayer, the plurality of layers further comprising a first polarizer thatis below the substantially transparent cover layer and a secondpolarizer that is below the substantially transparent cover layer and aliquid crystal layer, the display stack being configured to display acolor image; and a touch sensor within the display stack, the touchsensor comprising: a plurality of first conductive electrodes contactinga layer of a subset of the plurality of layers, the subset being belowthe substantially transparent cover layer; and a plurality of secondconductive electrodes contacting the layer of the subset of theplurality of layers; wherein the plurality of first conductiveelectrodes and the plurality of second conductive electrodes are locatedbetween the first polarizer and the second polarizer; wherein thedisplay stack is devoid of a polarizing layer between the first andsecond polarizers; wherein the plurality of first conductive electrodesand the plurality of second conductive electrodes are also in contactwith the first polarizer; and wherein: the plurality of first conductiveelectrodes comprise a plurality of drive electrodes; the plurality ofsecond conductive electrodes comprise a plurality of sense electrodes;and the plurality of drive electrodes and the plurality of senseelectrodes are also in contact with a same side of the first polarizer.2. The apparatus of claim 1, wherein: the display stack furthercomprises a color filter layer that is below the substantiallytransparent cover layer; and the subset of the plurality of layers isbetween the substantially transparent cover layer and the color filterlayer.
 3. The apparatus of claim 1, wherein: the display stack furthercomprises a color filter layer that is below the substantiallytransparent cover layer; and the subset of the plurality of layers isbelow both the substantially transparent cover layer and the colorfilter layer.
 4. The apparatus of claim 1, wherein the subset of theplurality of layers comprises a layer of non-birefringent material. 5.The apparatus of claim 1, wherein the display stack is a liquid crystaldisplay stack.
 6. The apparatus of claim 1, wherein the plurality offirst conductive electrodes and the plurality of second conductiveelectrodes comprise fine line metal electrodes.
 7. The apparatus ofclaim 1, wherein: the subset of the plurality of layers comprises onelayer; and the plurality of first conductive electrodes and theplurality of second conductive electrodes contact a same side of the onelayer.
 8. The apparatus of claim 1, wherein the display stack comprisesa flexible display stack and the touch sensor comprises a flexible touchsensor.
 9. The apparatus of claim 1, wherein the display stack with thetouch sensor provided therein is substantially free of air gaps.
 10. Anapparatus, comprising: a first polarizer disposed as a lower layer of adisplay stack for a touch-sensitive screen, the first polarizer beingconfigured to polarize light from a light source prior to that lightreaching a liquid crystal layer of the display stack, the liquid crystallayer located above the first polarizer in the display stack; asubstantially transparent cover layer disposed as a top layer of thedisplay stack, the substantially transparent cover layer beingconfigured to receive a touch input; a second polarizer disposed betweenthe first polarizer and the substantially transparent cover layer; atouch sensor located in the display stack between the first polarizerand the cover layer; wherein a plurality of electrodes of the touchsensor are located between the first polarizer and the second polarizer;wherein the display stack is devoid of a polarizing layer between thefirst and second polarizers; wherein the plurality of electrodes of thetouch sensor are in contact with the second polarizer; and wherein: theplurality of electrodes of the touch sensor comprise a plurality ofdrive electrodes and a plurality of sense electrodes; and the pluralityof drive electrodes and the plurality of sense electrodes are also incontact with a same side of the second polarizer.
 11. The apparatus ofclaim 10, wherein the layer of the display stack on which the pluralityof electrodes of the touch sensor are located comprises a layer ofnon-birefringent material.